tcg/optimize: Split out fold_ix_to_i

Pull the "op r, 0, b => movi r, 0" optimization into a function,
and use it in fold_shift.

Reviewed-by: Luis Pires <luis.pires@eldorado.org.br>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 10 insertions, 18 deletions

diff --git a/tcg/optimize.c b/tcg/optimize.c
index f5ab050..bf74b77 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -731,6 +731,15 @@ static bool fold_to_not(OptContext *ctx, TCGOp *op, int idx)
     return false;
 }
 
+/* If the binary operation has first argument @i, fold to @i. */
+static bool fold_ix_to_i(OptContext *ctx, TCGOp *op, uint64_t i)
+{
+    if (arg_is_const(op->args[1]) && arg_info(op->args[1])->val == i) {
+        return tcg_opt_gen_movi(ctx, op, op->args[0], i);
+    }
+    return false;
+}
+
 /* If the binary operation has first argument @i, fold to NOT. */
 static bool fold_ix_to_not(OptContext *ctx, TCGOp *op, uint64_t i)
 {
@@ -1384,6 +1393,7 @@ static bool fold_sextract(OptContext *ctx, TCGOp *op)
 static bool fold_shift(OptContext *ctx, TCGOp *op)
 {
     if (fold_const2(ctx, op) ||
+        fold_ix_to_i(ctx, op, 0) ||
         fold_xi_to_x(ctx, op, 0)) {
         return true;
     }
@@ -1552,24 +1562,6 @@ void tcg_optimize(TCGContext *s)
             break;
         }
 
-        /* Simplify expressions for "shift/rot r, 0, a => movi r, 0",
-           and "sub r, 0, a => neg r, a" case.  */
-        switch (opc) {
-        CASE_OP_32_64(shl):
-        CASE_OP_32_64(shr):
-        CASE_OP_32_64(sar):
-        CASE_OP_32_64(rotl):
-        CASE_OP_32_64(rotr):
-            if (arg_is_const(op->args[1])
-                && arg_info(op->args[1])->val == 0) {
-                tcg_opt_gen_movi(&ctx, op, op->args[0], 0);
-                continue;
-            }
-            break;
-        default:
-            break;
-        }
-
         /* Simplify using known-zero bits. Currently only ops with a single
            output argument is supported. */
         z_mask = -1;